1. Field of the Invention
The present invention relates, generally, to clutch assemblies and more specifically, to a bi-directional, axially applied pawl clutch assembly.
2. Description of the Related Art
Generally speaking, land vehicles require three basic components. These components include a power plant (such as an internal combustion engine), a power train and wheels. The power train""s main component is typically referred to as the xe2x80x9ctransmission.xe2x80x9d Engine torque and speed are converted in the transmission in accordance with the tractive-power demand of the vehicle. One-way clutches are frequently employed in transmissions, transfer cases, torque converters, and differentials to selectively transmit torque in one rotational direction, but not in the opposite rotational direction. To this end, one-way clutches typically include an inner race, an outer race, and an engagement mechanism disposed therebetween. The engagement mechanism is operable to lock the inner and outer races together thereby transmitting torque in one relative direction. The engagement mechanism is further operable to allow freewheeling rotation between the inner and outer races in the opposite rotational direction.
Engagement mechanisms commonly used in one-way clutches of the related art include pawls, sprags, and rollers. A cage, along with biasing members, such as springs, are also sometimes employed to retain the pawls, sprags, or rollers between the inner and outer races as well as to selectively assist in the change of operational modes between torque translation and freewheeling actuation of the clutch, depending on the direction of rotation between the inner and outer races. Where the engagement mechanism is a pawl, the pawls are often carried in pockets formed on the inner diameter of the outer race and are biased toward the rotational axis of the clutch assembly and into engagement with teeth formed on the outer diameter of the inner race. Alternatively, it is known in the related art to employ pawls that are moveable in the general direction of the axis of rotation of the clutch assembly between a drive and driven member of a one-way clutch to translate torque therebetween.
In addition to one-way clutches, bi-directional overrunning clutches have also been proposed in the related art. These bi-directional overrunning clutch assemblies typically employ an inner race, an outer race, and a plurality of rollers as the engagement mechanism disposed therebetween. The bi-directional overrunning clutches generally known in the related art are typically designed to be self-actuating. However, these self-actuating bi-directional overrunning clutches are relatively mechanically complex and have certain physical limitations and drawbacks. For example, the inner and outer race must rotate relative to one another over a relatively large angular distance between an engaged position in one rotational direction and the engaged position in the opposite rotational direction. Unfortunately, this relatively large angular movement between the inner and outer races causes relatively hard lock-ups during transitions where the direction of torque translation is reversed and thus produces undesirable driving conditions. In addition, the relatively abrupt, hard lock-ups also tend to shorten the useful mechanical life of the clutch assembly due to the severe impact forces that are generated between transitional engagements. Moreover, the self-actuating bi-directional clutches known in the related art generally suffer from the disadvantage that they cannot be selectively engaged in an efficient manner or to optimize the vehicle power output in response to varying driving conditions. For these reasons, the bi-directional overrunning clutch assemblies known in the related art have not been widely employed in transmissions, transfer cases, and differentials.
Accordingly, there remains a need in the art for a bi-directional clutch that can be selectively actuated and controlled in a manner to provide driving comfort and offer efficient operating modes for various driving conditions. Furthermore, there remains a need in the art for a controllable bi-directional overrunning clutch assembly that can provide both torque translation and freewheeling operation in either rotational direction. In addition, there remains a need in the art for a bi-directional clutch assembly that can be effectively shifted between various operational modes without jamming of the engagement mechanism or other failures occurring at the interface between the races of the clutch assembly.
The present invention overcomes the disadvantages of the related art in a bi-directional overrunning clutch assembly including a drive member that is rotatable about an axis and a pair of driven members that is similarly rotatable about the axis of rotation. The pair of driven members are disposed on either side of the drive member such that each one of the pair of driven members is in side-by-side confronting relationship with the drive member. In addition, the clutch assembly includes first and second engagement mechanisms. The first engagement mechanism is supported between the confronting surfaces of the drive member and one of the driven members. The second engagement mechanism is supported between the confronting surfaces of the drive member and the other driven member. The first engagement mechanism is operable to be deployed between a disengaged position allowing relative rotation between the drive member and the driven member associated with the first engagement mechanism and an engaged position where the first engagement mechanism acts to translate torque between the drive member and the associated driven member in one rotational direction. On the other hand, the second engagement mechanism is operable to be deployed between a disengaged position allowing relative rotation between the drive member and the driven member associated with the second engagement mechanism and an engaged position where the second engagement mechanism acts to translate torque between the drive member and the associated driven member in the opposite rotational direction translated with respect to the first engagement mechanism. Furthermore, the bi-directional overrunning clutch assembly of the present invention includes a pair of actuators that are associated with the first and second engagement mechanisms. Each actuator is operable to move its associated engagement mechanism in an axial direction between the disengaged and engaged positions.
In this way, the present invention provides a bi-directional clutch that can be selectively actuated and controlled in a manner to provide driving comfort and offer efficient operational modes for various driving conditions. Furthermore, the bi-directional overrunning clutch assembly of the present invention is controllable such that it can provide both torque translation and freewheeling operation in either rotational direction. In addition, the bi-directional overrunning clutch assembly of the present invention can be effectively shifted between various operational modes without jamming of the engagement mechanisms or other failures occurring at the interface between the drive member and the two driven members associated with the drive member. Finally, the bi-directional overrunning clutch assembly of the present invention is mechanically simple, cost effective to manufacture, and overcomes the deficiencies in the related art in an efficient manner.